explorer: Explorer
In DavidBarke/shinyExplorer: Explorer and Contextmenu for Shiny apps

Shiny module representing an explorer usable for selecting elements of different kinds and invoking actions on them.

explorer_ui(id)

explorer(
  input,
  output,
  session,
  .values,
  .root_node_r,
  .explorer_classes = list(),
  addable_r = shiny::reactive("__group__"),
  visible_r = shiny::reactive("__group__"),
  .display_header = TRUE,
  .label_list = label_explorer(),
  .state = list()
)

`id`	The module's id.
`input, output, session`	Called by `callModule`.
`.values`	The `.values` list.
`.root_node_r`	A `reactive` returning an object of class `ExplorerNode`. This needs not necessarily to be the root node of an object of class `ExplorerTree`.
`.explorer_classes`	A `list` of objects of class `ExplorerClass`.
`addable_r`	A `reactive` returning a `character` vector containing the labels of explorer classes that are addable to the explorer.
`visible_r`	A `reactive` returning a `character` vector containing the labels of explorer classes that are displayed to the user.
`.display_header`	If `TRUE`, the navigation header is displayed, otherwise it is not.
`.label_list`	A `list` created with `label_explorer` containing labels for all buttons used inside the explorer module.
`.state`	A `list` which is passed to every explorer class server function. Use this list to implement special behaviour of an explorer class dependent on conditions outside of the explorer.

The explorer module returns a list containing the following reactives, that you may access in the calling server function.

`contextmenued_node_r`	An object of class `ExplorerNode`. This is the node, which has been last contextmenued.
`current_node_r`	An object of class `ExplorerNode`. This is the node, whose children are currently displayed in the explorer's datatable. `selected_child_node_r` An object of class `ExplorerNode`. This is the node, which has been last clicked.